This invention relates to pressure cylinders and more particularly to a pressure cylinder of the hydraulic or pneumatic type in which a piston is movable within the bore of a cylinder housing to perform a work operation.
Pressure cylinders have been available for many years and have been employed in a multitude of work applications to perform a multitude of work operations. In a typical pressure cylinder, the cylinder housing defines an elongated bore, a piston is reciprocally mounted within the bore, and a piston rod extends from the piston and through an opening in the forward end wall of the cylinder housing to provide a free end of the piston rod which is available to perform the work operation.
Whereas pressure cylinders of this general type are generally satisfactory, they suffer from several disadvantages. Specifically, they are in general unable to handle offset loading on the piston rod because of the limited sliding interface between the piston and the bore of the cylinder housing; it is difficult to provide switches to determine the limits of the movement of the piston since it is necessary to seal the switches with respect to the pressure fluid contained within the bore of the cylinder housing; the rod seal at the interface of the piston rod and the forward end wall of the cylinder experiences heavy loading and as a result requires frequent replacement; the useful life of the rod seal is further limited by debris that is introduced into the seal by the reciprocal movement of the piston rod; in the case where the piston rod is used to raise a load the raised load must be propped up by auxiliary support means since the surface area of the piston rod is inadequate to provide a stable support for the raised load; and, for a given stroke, the overall height of the pressure cylinder tends to be rather long with the result that the cylinder cannot be utilized in situations where working space is limited.